Update filters on refreshDisplay and remember old selecttions

Update the filters if the list of dives is updated by calling
MultiFilterSortModel::instance()->myInvalidate();
This had the side effect of clearing all selections. Thus, in
the repopulate() methods of the FilterModels, check those
entries that were checked previously. Since all the filter
models use the same code, introduce a base class FilterModelBase.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

qt-models/filtermodels.cpp

@@ -78,7 +78,40 @@ CREATE_COMMON_METHODS_FOR_FILTER(SuitsFilterModel, count_dives_with_suit)
 
 CREATE_INSTANCE_METHOD(MultiFilterSortModel)
 
-SuitsFilterModel::SuitsFilterModel(QObject *parent) : QStringListModel(parent)
+FilterModelBase::FilterModelBase(QObject *parent) : QStringListModel(parent)
+{
+}
+
+// Update the stringList and the checkState array.
+// The last item is supposed to be the "Show Empty Tags" entry.
+void FilterModelBase::updateList(const QStringList &newList)
+{
+	// Keep copy of old checkState array to reimport them later.
+	std::vector<char> oldCheckState = checkState;
+	checkState.resize(newList.count());
+	std::fill(checkState.begin(), checkState.end(), false);
+	anyChecked = false;
+
+	// Ignore last item, since this is the "Show Empty Tags" entry.
+	for (int i = 0; i < rowCount() - 1; i++) {
+		if (oldCheckState[i]) {
+			int ind = newList.indexOf(stringList()[i]);
+			if (ind >= 0 && ind < newList.count() - 1) {
+				checkState[ind] = true;
+				anyChecked = true;
+			}
+		}
+	}
+
+	// On program startup, the old list is empty.
+	if (rowCount() > 0 && oldCheckState.back()) {
+		checkState.back() = true;
+		anyChecked = true;
+	}
+	setStringList(newList);
+}
+
+SuitsFilterModel::SuitsFilterModel(QObject *parent) : FilterModelBase(parent)
 {
 }
 
@@ -127,13 +160,10 @@ void SuitsFilterModel::repopulate()
 	}
 	qSort(list);
 	list << tr("No suit set");
-	setStringList(list);
-	checkState.resize(list.count());
-	std::fill(checkState.begin(), checkState.end(), false);
-	anyChecked = false;
+	updateList(list);
 }
 
-TagFilterModel::TagFilterModel(QObject *parent) : QStringListModel(parent)
+TagFilterModel::TagFilterModel(QObject *parent) : FilterModelBase(parent)
 {
 }
 
@@ -150,10 +180,7 @@ void TagFilterModel::repopulate()
 	}
 	qSort(list);
 	list << tr("Empty tags");
-	setStringList(list);
-	checkState.resize(list.count());
-	std::fill(checkState.begin(), checkState.end(), false);
-	anyChecked = false;
+	updateList(list);
 }
 
 bool TagFilterModel::doFilter(dive *d, QModelIndex &index0, QAbstractItemModel *sourceModel) const
@@ -190,7 +217,7 @@ bool TagFilterModel::doFilter(dive *d, QModelIndex &index0, QAbstractItemModel *
 	return false;
 }
 
-BuddyFilterModel::BuddyFilterModel(QObject *parent) : QStringListModel(parent)
+BuddyFilterModel::BuddyFilterModel(QObject *parent) : FilterModelBase(parent)
 {
 }
 
@@ -243,13 +270,10 @@ void BuddyFilterModel::repopulate()
 	}
 	qSort(list);
 	list << tr("No buddies");
-	setStringList(list);
-	checkState.resize(list.count());
-	std::fill(checkState.begin(), checkState.end(), false);
-	anyChecked = false;
+	updateList(list);
 }
 
-LocationFilterModel::LocationFilterModel(QObject *parent) : QStringListModel(parent)
+LocationFilterModel::LocationFilterModel(QObject *parent) : FilterModelBase(parent)
 {
 }
 
@@ -294,10 +318,7 @@ void LocationFilterModel::repopulate()
 	}
 	qSort(list);
 	list << tr("No location set");
-	setStringList(list);
-	checkState.resize(list.count());
-	std::fill(checkState.begin(), checkState.end(), false);
-	anyChecked = false;
+	updateList(list);
 }
 
 MultiFilterSortModel::MultiFilterSortModel(QObject *parent) :